<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 
        indexOf(value) 根据值查找对应的下标
        includes 是否包含某位(多位)字符
     -->
    <script>
        var arr = "hello"
        console.log(arr.indexOf('e')); // 1
        console.log(arr.includes("eh")); //false
    </script>
</body>
</html>